This study will evaluate the ease and reliability of Raman scattering spectroscopy, a new
technique to measure the amount of the pigment lutein in the retina, the light-sensitive
tissue lining the back of the eye. The highest concentrations of lutein are in the center
of the retina, called the macula, which is the area most important for fine, detailed
vision. The functions of lutein are not fully known. Besides absorbing blue light, it may
help protect against abnormal changes in the retina, such as age-related macular
degeneration. Until recently, lutein was measured using long, cumbersome, and difficult
tests. This study will evaluate a new instrument that provides faster measurements. It
will be tested under different conditions, such as wearing or not wearing glasses or contact
lenses, or dilating or not dilating the pupil of the eye.
Healthy normal volunteers between 20 and 65 years of age may be eligible for this study,
which involves two visits to the NIH Clinical Center, as follows:
Visit 1 - Screening
- Medical history and physical examination, including measurement of vital signs (blood
pressure, pulse, temperature, and breathing rate), and examination of the head and
neck, heart and lungs, and arms and legs.
- Eye examination, including eye chart test, eye pressure measurement, examination of
pupils and eye movements, and examination of the retina (back part of the eye) using a
strong light and magnifying lens after dilation of the pupils.
- Raman scattering spectroscopy to measure lutein. For this test, the subject looks with
one eye at a brief, bright flash of bluish light (similar to a flashbulb light) from a
laser. This is repeated several times. Subjects who wear glasses or contact lenses
for distance vision will be tested without them and then again with a lens in front of
the eye. Subjects who do not wear glasses or contact lenses will be tested before and
after dilation of the pupil.
- Contrast sensitivity to assess ability to identify an object from the background and to
see everyday objects. The subject looks at and identifies a variety of objects of
different shapes and sizes.
- Color vision to determine the ability to identify different shades of color. The
subject arranges a line of colorful discs, similar to checkers, in order of similar
Visit 2 - Repeat Spectroscopy
Subjects return 1 week after the screening visit for a repeat Raman scattering spectroscopy
to evaluate the precision of the measurements.
The primary objective of this study is to evaluate the degree of variability in retinal
measurements of lutein, a carotenoid macular pigment of human retina in normal volunteers,
with a new and novel technique of resonant Raman scattering spectroscopy. This technique is
generally more objective than psychophysical techniques used for lutein measurements, such
as heterochromatic flicker photometry. Raman scattering spectroscopy is non-invasive and
the levels of ocular exposure to argon laser light used in this technique are well below the
safety limits recommended by the American National Standards Institute.
1. Men and women between 18 and 75 years of age.
2. Corrected visual acuity of 20/30 or better.
3. Ability to understand and sign an informed consent form prior to enrollment.
1. Ocular disease, including significant explained or unexplained visual field loss.
2. Ocular media opacities.
3. History of epilepsy or light-triggered convulsions.
4. A maximal pupillary dilation of less than 7 mm.